The present disclosure generally relates to a method and system for heating or cooking a product utilizing steam. More particularly, the present disclosure relates to a system and method that control the pressure of steam, the amount of steam injected into the product flow and the pressure of the product flow to repeatably control the shear imparted on the product flow.
Current direct steam injection technologies either modulate the pressure of the steam being injected into a product flow as a means of controlling the temperature of the product flow or control the size of the steam orifice to control the amount of steam injected into the product flow. Each of these two technologies has several disadvantages for temperature control.
In the first scenario that modulates the steam pressure, the effects of pressure changes are not instantaneous and need a short amount of time to re-equilibrate to changing conditions. This leads to the temperature variation of the product flow when flow rates change or when plant steam pressure supplies change during production. These temperature fluctuations can lead to product damage or loss of aseptic conditions in a food production process.
Secondly, the shear imparted on the food from the velocity of the steam impacting the process fluid cannot be changed. For any given pressure, there is a set velocity of steam penetration, and thereby shear effects. Changing the pressure will change the shear effects but will also change the temperature of the product flow.
Third, very low pressure differentials are required in order to achieve the desired temperature for the product flow without over heating the product flow. These relatively low pressure differentials do not allow the steam to reach a high enough velocity to create high shear conditions. This reduces the ability for devices that utilize this method to be able mix, emulsify and vigorously cook foods which need high shear.
In the second scenario in which the size of the steam orifice is modified, the process is very stable and responsive to changing conditions; however, the shear imparted on the fluid can be significant and damaging when a greater temperature change is desired and more steam must be introduced into the product flow.